I'm a headphone junkie. I'm not an audiophile but I am in love with great sound. My favorite set are AudioTechnica ATH A50s, teamed up with a Fiio E11 head amp. I have at least 6 pairs of Ableplanets- all with active noise cancelling. In the gym or doing homework or at work- they do the job. The only problem is that they are not portable- even my gym pair N200s, are bulky and weird looking. They really beat, and I am taken completely into my own world, so I like them. The lifetime warranty is what makes all of the sets a no-brainer.
These are the only truly portable pair I've seen or owned. They pack a lot of sound, and they're comfortable and small. They may actually replace my gym headphones. These do not use external powered active noise cancelling, so you don't need a battery. They aren't the loudest or clearest, but for the price point, they're incredibly well made and give great sound.
You can walk around town with these and not draw attention. I love that. They're really solid and you're not going to get better sound for the size/price. They're a $50 set for less than half of that. I'll definitely get another pair.